Cold heading formed wedge for use in post tensioning concrete

ABSTRACT

A wedge for use in post tensioning concrete is formed by cold heading. The cold heading operation may include providing a wire, feeding the end of the wire into a cold heading apparatus, cold heading the end of the wire to form at least one wedge blank, and finishing the wedge blank to form the wedge.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a nonprovisional application which claims priority from U.S. provisional application No. 62/200,994, filed Aug. 4, 2015, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD/FIELD OF THE DISCLOSURE

The present disclosure relates generally to post-tensioned, pre-stressed concrete construction. The present disclosure relates specifically to wedges for anchors for use therein.

BACKGROUND OF THE DISCLOSURE

Many structures are built using concrete, including, for instance, buildings, parking structures, apartments, condominiums, hotels, mixed-use buildings, casinos, hospitals, medical buildings, government buildings, research/academic institutions, industrial buildings, malls, bridges, pavement, tanks, reservoirs, silos, foundations, sports courts, and other structures.

Pre-stressed concrete is structural concrete in which internal stresses are introduced to reduce potential tensile stresses in the concrete resulting from applied loads. This can be accomplished by two methods—post-tensioned pre-stressing and pre-tensioned pre-stressing. When post-tensioning concrete, the pre-stressing assembly is tensioned after the concrete has attained a specified strength. The pre-stressing assembly, commonly known as a tendon, may include for example and without limitation, anchorages, one or more strands, and sheathes or ducts. The strand is tensioned between anchors which are embedded in the concrete once the concrete has hardened. The strand may be formed from a metal or composite or any suitable material exhibiting tensile strength which can be elongated including, for example and without limitation, reinforcing steel, single wire cable, or multi-wire cable. The strand is typically fixedly coupled to a fixed anchorage positioned at one end of the tendon, the so-called “fixed end”, and is adapted to be stressed at the other anchor, the “stressing end” of the tendon. The strand is generally held to each anchor by one or more wedges. Typically, anchors include a tapered recess which, when the strand is placed under tension, cause the wedges to further engage the strand. Wedges are typically made of metal.

SUMMARY

The present disclosure provides for a method for forming a wedge for post tensioning concrete. The method may include providing a wire; feeding a portion of the wire into a cold heading apparatus; cold heading a portion of the wire to form at least one wedge blank; and finishing the wedge blank to form the wedge.

The present disclosure further provides for a method including providing a wire and feeding a portion of the wire into a cold heading apparatus. The method also includes cold heading a portion of the wire to form at least one wedge blank and finishing the wedge blank to form the wedge. The method includes providing an anchor for post tensioning concrete, threading a strand through the anchor, and positioning the wedge on the strand.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 depicts a cross section of an anchor having a wedge consistent with at least one embodiment of the present disclosure.

FIG. 2 depicts a block diagram of a cold heading procedure for forming wedges consistent with at least one embodiment of the present disclosure.

FIGS. 3A-D depict an overview of a cold heading process for forming wedges consistent with at least one embodiment of the present disclosure.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

FIG. 1 depicts anchor 10 for use in post tensioning concrete. Anchor 10 is adapted to receive and couple to strand 12 of tendon 14. During installation, strand 12 may be threaded through anchor 10. Strand 12 may be, for example and without limitation, mono-wire cable or multi-wire cable. For the purposes of this disclosure, the axis parallel with the length of strand 12 will be referred to as the longitudinal axis of strand 12. Anchor 10 may include anchor body 16 adapted to retain the position of anchor 10 when positioned in formed concrete.

Anchor 10 may couple to strand 12 by the use of one or more wedges 100. Wedges 100 may be substantially wedge shaped and adapted to fit into a tapered recess 18 formed in anchor body 16. During use, wedges 100 may be installed to the strand in a direction perpendicular to the longitudinal axis of the strand. Tension on strand 12 may cause wedges 100 to move into tapered recess 18, applying a gripping force on strand 12.

In some embodiments, wedges 100 may be formed by cold heading. FIG. 2 depicts a block diagram of a cold heading process. Wire 101 is provided on spool 103. Wire 101 is fed by one or more drive wheels (not shown) into cold heading apparatus 105. In some embodiments, cold heading apparatus 105 may include straightening apparatus 107 which may include a plurality of rollers adapted to straighten wire 101 as it enters cold heading apparatus 105. Wire 101 may be fed to forming dies 109. Forming dies 109 reshape a portion of wire 101 progressively into the final form of one or more wedge blanks 113. At some point in the cold heading operation, a portion of wire 101 is separated 111 from the rest of wire 101, separating the one or more formed wedge blanks 113.

As depicted in FIGS. 3A-D, forming dies 109 a-f may be utilized to progressively reshape a portion of wire 101 by cold heading. FIGS. 3A-D depict the cold heading operation as a 3-step operation, but one having ordinary skill in the art with the benefit of this disclosure will understand that any number of operations may be undertaken to cold head wedge blanks 113. The following discussion is merely exemplary of a cold heading operation consistent with at least one embodiment of the present disclosure.

As depicted in FIG. 3A, wire 101 is fed through forming die 109 a. Wire portion 115 is formed between forming die 109 a and 109 b to initially reshape wire portion 115. In this embodiment, a portion of wire 101 is separated from wire 101 at this stage by, for example, shear cutter 117 to be formed into wedge blank 113. As depicted in FIG. 3B, forming dies 109 c, 109 d further refine the shape of wire portion 115. In this embodiment, two wedge blanks 113 are formed simultaneously from wire portion 115. One having ordinary skill in the art with the benefit of this disclosure will understand that any number of wedge blanks 113 may be formed from wire portion 115. As depicted in FIG. 3C, forming dies 109 e, 109 f further refine the shape of wedge blanks 113 into the final cold headed form shown in FIG. 3D. As understood by one having ordinary skill in the art with the benefit of this disclosure, forming dies 109 a-f may operate by stamping, swaging, punching, forging, extruding, upsetting, or a combination thereof.

In some embodiments, wedge blanks 113 may emerge from the cold heading process in a final form requiring no additional treatment. In some embodiments, wedge blanks 113 may be further processed as shown in FIG. 2 as further treatment 119. For example, in some embodiments, wedge blanks 113 may be tumbled or otherwise polished to improve their surface finish. In some embodiments, wedge blanks 113 may be given a surface treatment or may be heat treated, hardened, or tempered. In some embodiments, wedge blanks 113 may be further machined to, for example and without limitation, add grooves.

The foregoing outlines features of several embodiments so that a person of ordinary skill in the art may better understand the aspects of the present disclosure. Such features may be replaced by any one of numerous equivalent alternatives, only some of which are disclosed herein. One of ordinary skill in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. One of ordinary skill in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

1. A method for forming a wedge for post tensioning concrete comprising: providing a wire; feeding a portion of the wire into a cold heading apparatus; cold heading a portion of the wire to form at least one wedge blank; and finishing the wedge blank to form the wedge.
 2. The method of claim 1, wherein cold heading a portion of the wire to form at least one wedge blank comprises: feeding the portion of the wire between a first and second forming die; reshaping the portion of the wire by the first and second forming die; and separating the portion of the wire from the wire to form the at least one wedge blank.
 3. The method of claim 2, wherein reshaping the portion of the wire by the first and second forming die comprises one or more of stamping, swaging, punching, forging, extruding, or upsetting the portion of the wire.
 4. The method of claim 2, further comprising further reshaping the portion of the wire by a third and fourth forming die.
 5. The method of claim 1, wherein finishing the wedge blank to form the wedge comprises one or more of tumbling, polishing, heat treating, hardening, tempering, grooving, or surface treating the wedge blank.
 6. The method of claim 1, wherein the process of feeding the wire to the cold heading apparatus is performed by one or more drive wheels.
 7. The method of claim 6, wherein the cold heading apparatus further includes a straightening apparatus, the straightening apparatus including a plurality of rollers.
 8. The method of claim 1, wherein two wedge blanks are formed simultaneously.
 9. The method of claim 1 further comprising machining the wedge blanks to form grooves.
 10. A method comprising: providing a wire; feeding a portion of the wire into a cold heading apparatus; cold heading a portion of the wire to form at least one wedge blank; finishing the wedge blank to form the wedge; providing an anchor for post tensioning concrete; threading a strand through the anchor; and positioning the wedge on the strand.
 11. The method of claim 10, wherein positioning the wedge is on the strand is in a direction perpendicular to the longitudinal axis of the strand.
 12. The method of claim 10, wherein cold heading a portion of the wire to form at least one wedge blank comprises: feeding the portion of the wire between a first and second forming die; reshaping the portion of the wire by the first and second forming die; separating the portion of the wire from the wire to form the at least one wedge blank.
 13. The method of claim 12, wherein reshaping the portion of the wire by the first and second forming die comprises one or more of stamping, swaging, punching, forging, extruding, or upsetting the portion of the wire.
 14. The method of claim 12, further comprising further reshaping the portion of the wire by a third and fourth forming die.
 15. The method of claim 10, wherein finishing the wedge blank to form the wedge comprises one or more of tumbling, polishing, heat treating, hardening, tempering, grooving, or surface treating the wedge blank.
 16. The method of claim 10 further comprising moving the wedge into a tapered recess.
 17. The method of claim 16 further comprising applying a gripping force using the wedges on the strand.
 18. The method of claim 10, wherein the wedges have grooves. 